The present invention relates to an electronic device equipped with a touch panel.
As widely known, a touch panel is a combination of a display device such as a liquid crystal panel and a touch pad (a position input device).
Touch panels include a capacitance type touch panel that can be operated at a height in a predetermined range (hereinafter, this proximity operation will be referred to as a “hover operation”) without touching a panel surface with a finger. FIG. 11 is a diagram illustrating a schematic configuration of a capacitance type touch panel. In FIG. 11, a transmission electrode 101 and a reception electrode 102 are disposed on a bottom surface of a plate-like dielectric body 100 so as to be separated from each other, and a driving pulse is applied to the transmission electrode 101 from a driving buffer 103. When the driving pulse is applied, an electric field is generated. When a hand enters the electric field, the number of electric force lines between the transmission electrode 101 and the reception electrode 102 is decreased. A change in the number of electric force lines appears as a change in charges in the reception electrode 102. It is possible to detect the approach of the hand to the touch panel, from the change in charges in the reception electrode 102.
FIGS. 12A to 12C are diagrams illustrating a detection state of a finger when a hand is gradually brought close to a touch panel. FIG. 12A illustrates a state where a hand is away from an electric field, FIG. 12B is a finger hover detection state when the finger enters the electric field, and FIG. 12C is a finger touch detection state when the finger completely enters the electric field and touches the touch panel.
Meanwhile, a method of bringing a finger into contact with a panel surface is disclosed in, for example, Patent Document JP-A-2011-138278. A proximity detection apparatus disclosed in Patent Document JP-A-2011-138278 includes a plurality of electrodes having capacitance that changes by approach and touch of an object to be detected, an electrode control unit that subsequently couples the plurality of electrodes while shifting electrodes having any number of electrodes coupled by any number of slide electrodes so that some of the electrodes overlap each other, to form the electrodes as coupling electrodes, respectively, a capacitance detection unit that detects capacitance of the coupling electrodes coupled by the electrode control unit, and a position calculation unit that calculates an approach or touch position of the object to be detected, on the basis of the capacitance detected by the capacitance detection unit.